Hello,
If you notice in 1870 there are only two
Everett's in Panola, Tx. One white female and
Jacob Everett, black male, who has a 13 y/o
male son, named Jonas. Jonas could be a
nickname that Amos was called at that time, or Amos is the nickname that stuck.
Maybe, Jonas is twin brother and Amos was
away working when the census was taken.
You may want to check other spellings of the
name Everett.
I hope this can help you.

Greg